Durability Options

Databases in TimesTen are persistent across power failures and crashes. TimesTen accomplishes durability by periodically saving to disk.

• Checkpoint files: A checkpoint operation writes the current database image to a checkpoint file on the file system, which has the effect of making all transactions that committed before the checkpoint durable.

• Transaction log files: For transactions that committed after the last checkpoint, TimesTen uses conventional logging techniques to make them durable. As each transaction progresses, it records its database modifications in an in-memory transaction log. At commit time, the relevant portion of the transaction log is flushed to the file system. This log flush operation makes that transaction, and all previously-committed transactions, durable.

  Control returns to the application after the transaction log data has been durably written to the file system. A durably committed transaction is not lost even in the event of a system failure.

Any recovery uses the last checkpoint image together with the transaction log to reconstruct the latest transaction-consistent state of the database.

When committing transactions, TimesTen reduces the performance cost for durable commits with a group commit of multiple concurrently running transactions. TimesTen performs a single file system write operation to commit a group of concurrent transactions durably. Group commit does not improve the response time of any given commit operation, as each durable commit must wait for the file system write operation to complete, but it can significantly improve the throughput of a series of concurrent transactions.

See Durability for TimesTen for the durability implementation options for TimesTen.